Field-magnet.



E. VOLKERS.

FIELD MAGNET.

APPLICATION rum) MAR.27, 1911.

WA I

Patented Feb. 11, 1913.

EMIL VOLKERS, OF BERLIN, GERMANY.

FIELD-MAGNET.

Specification of Letters Patent.

Patented Feb. 11, 1913.

Application filed March 27, 1911. Serial No. 617,246.

To all whom it may concern:

Be it known that I, EMiL VOLKERS, a subject of the German Emperor, residing at 3336 Liitzowstrasse, Berlin, IV. #35, Germany, engineer, have invented a Field-Magnet, of which the following is a specifica-- tion.

The use of multipolar electrical machines, having a stationary outer armature and inner rotating field magnet, as igniting ma chine for explosion motors is greatly increased if the number of poles is increased as in this manner the required lowest speed can be conveniently obtained and the capability of control is increased. The required increase of the number of poles is limited by the increase of magnetic leakage, so that the best efliciency for each type of field magnet of certain dimensions, is obtained with a certain number of poles.

This invention relates to a method of increasing the number of poles in the construction of the field magnet and consists in constructing the magnet of a central part and two pole pieces connected to the ends thereof.

In the accompanying drawing is shown a constructional form of the invention.

Figures 1 and 2 show a star shaped magnet in longitudinal section and front elevation respectively. Fig. 3 is a perspective view of the essential parts required for the construction of the magnet. Fig. 4 is a front elevation of a modified form.

According to the first constructional form the shaft a, which is advantageously pro vided of bronze, is formed with two 61rlargements b which serve to support the body prop-er of the field magnet. On these enlargements is mounted the central member c which forms the connection between the pole pieces (Z and e. For the purpose of securing the separate end pole pieces in position and for the purpose of connecting them to the central member, two rings f and g each having suitable notches h are provided one at each end of the central member. The pole pieces are connected to the central member by first fitting the two rings 7 and g on the parts which are placed together to form the central member, then inserting the pole pieces into the notches it provided in the rings 7 and g and then placing the outer iron rings z' in position. In this case it is unnecessary to provide the central member 0 and the pole pieces of sheet steel of the same thickness, but the central member 0 can be laminated in the same manner as a commutator (Fig. 2) so as to economize the space as much as possible.

According to the above described construction the central member 0 consists of a number of parts placed side by side in the same manner as the separate strips of a longitudinally divided tube but it can also be provided in the form of a cylinder consisting of one integral part as shown in Figs. 3 and 4. Here again the rings 2' are placed around the ends of the pole pieces at and e which are inserted in the notches h in the manner hereinbefore described. The ends of the pole pieces are thus secured in position between the rings 6, f and g which form the connection between the central member 0 and the pole pieces d and e, for the passage of the magnetic flux. It may also be advantageous to cut the rings 7 and g at is (Fig. 2) so as to produce a spring effect. The ends of the pole ieces are then placed between the rings 7, g and i and the tubular central member 0 is then forced into these. The rings 7 and g are thus slightly expanded and the pole pieces are thereby securely fixed in position by the additional pressure.

In comparison with the known construction of star shaped magnets the present invention offers various advantages :The total cross section within an equal space, of the parts through which the magnetic flux passes is greater, all the parts can be made of material which is the'most suitable for the required purpose, for example of various kinds of iron, and by providing the separate parts of normal size the production and assembling is more convenient and inexpensive; finally the field magnet can be provided with a previously wound magnetizing coil, which surrounds the central member.

lVhat I claim as my invention and desire to secure by Letters Patent is An inner field magnet for multipolar electrical machines comprising a shaft, enlarged portions on said shaft, a central member disposed on said enlarged portions, 111 testimony whereof I have hereunto notched rings at each end of said central signed my name to this specification in the member, pole pieces mounted in the notches presence of two subscribing witnesses.

of said rings, the pole pieces in one ring EMIL VOLKERS. projecting between the pole pieces of the other ring, and means for securing the pole pieces in the notches of said rings.

Vitnesses HENRY HAsPER,

WOLDEMAR HAUPT.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

